Though the present invention is well characterized as a low power flow measuring device, the term "flow meter" is used herein for its simplicity and relationship to flow measuring.
As a flow meter, the low power flow meter of the present invention has many applications, some of which are discussed in more detail below and others of which are apparent from the description herein. A principle application, however, of the present invention is for water flow monitoring in irrigation systems, municipal water/sewer systems, environmental data collection and the like.
In this context, the present invention is particularly useful in arid regions, such as the American west, where water is scarce and the need to accurately measure and appropriately distribute water is of paramount importance. Currently, the division of water between agriculture, municipalities and environmental concerns is being reconsidered and new priorities established. Also, concepts such as a water market are being discussed. To facilitate appropriate resolution of these current concerns and corresponding future concerns, it is essential that technology be developed for accurately and efficiently measuring the use of our existing water supply. To achieve this end, measurements must be done with sufficient frequency, at distributed sites throughout a water system (i.e., including remote locations) and in an affordable manner. The collected data must also be readily available.
In response to this need, a plurality of water monitoring devices have been developed. These include multi-parameter and single-parameter data logging devices. To access remote locations, devices have been developed that are battery powered and, therefore, operate autonomously at the location in a water system where they are placed. A standard one of these prior art meters contains a sensor, a processor, memory and a display. Data is recovered in at least one embodiment by reading the display. In other embodiments, data may be recovered by transfer to a memory card or by download to an IBM-compatible computer.
Though known flow meters have made a significant contribution to the art, they are disadvantageous in that they are not sufficiently low power devices. As such they drain battery power relatively rapidly and provide either extended field life with very infrequent sampling or frequent sampling with a brief field life, where field life refers to the period of use between battery replacements.
One example of this type of device is a known flow meter that is capable of sampling once daily for approximately a year. One sample in 24 hours, however, is inappropriately long in many applications. For example, in the context of irrigation flumes, it is necessary to measure water flows every few minutes or less to accurately monitor flow and determine use. This known flow meter would last only a few days sampling at a requisite frequency. Such a short field life, or even a field life of a few months, would necessitate a disadvantageous expense for the purchase of new batteries and a disadvantageous use of labor to physically replace the batteries in all meters in a water system.
Furthermore, as higher sampling rates are achieved in extended field life devices, a need exist for means that efficiently transfer the increased amounts of collected data from the flow meter. This means must also be capable of operating in an extremely low power manner.